Method and apparatus for producing molecular film

ABSTRACT

A method for forming a molecular film includes the steps of: coating a surface of a substrate having active hydrogen atoms on its surface with a coating solution containing a silane-based compound having at least one reactive group selected from the group consisting of a chloro group, an alkoxy group and an isocyanate group; and effecting an elimination reaction between the active hydrogen atoms on the surface of the substrate and reactive groups of the silane-based compound, thereby covalently bonding the silane-based compounds to the surface of the substrate. The substrate is supplied to a chamber in which an atmosphere is maintained at a low water vapor density. The surface of the substrate is coated with a coating solution containing the silane-based compound and a solvent by using a transfer element. A dehydrochlorination reaction is effected between the active hydrogen atoms and the chloro groups of the silane-based compounds. Thereafter, any coating solution containing unreacted silane-based compounds after coating is removed inside or outside the chamber.

FIELD OF THE INVENTION

The present invention relates to a method and an apparatus for producinga molecular film in which silane-based compounds are covalently bondedto a substrate surface via siloxane bonds.

BACKGROUND OF THE INVENTION

A method for producing a molecular film by coating the surface of aglass or the like having active hydrogen atoms on its surface withchlorosilane-based compounds having chlorosilyl groups at the end of themolecules comprising alkyl groups or fluoroalkyl groups so as to formcovalent bonds by a dehydrochlorination reaction already has beenproposed.

In the prior art, a substrate is dipped into a coating solutioncontaining chlorosilane-based compounds to form a molecular film, asdisclosed in Japanese Laid-Open Patent Publication No. 1-70917 and EP0492545A. Another example of the proposed methods is to contact thechlorosilane-based compounds in a vapor phase onto the surface of asubstrate for effecting a reaction.

However, the conventional dip method is excellent in the case where afilm is to be formed not on a flat plate, but instead on a roughsurface, because the liquid reacts along the rough surface, so that afilm can be formed along the surface of the unusual shaped object. Onthe other hand, this method requires a large amount of the liquid fordipping and a troublesome operation of putting in and withdrawing thesubstrate, which takes a long time. Consequently, this method adverselyresults in a high cost. Furthermore, since the chlorosilane-basedcompounds readily react with water, the pot life is short. In addition,in the dip method, the chlorosilane-based compounds are in contact withthe entire substrate and a reaction is effected all over the surface ofthe substrate. Therefore, this method is disadvantageous in the casewhere a prescribed portion is not desired to be coated with thechlorosilane-based compounds.

Furthermore, a method of contacting the chlorosilane-based compound in avapor phase with the surface of the substrate for effecting a reactionis disadvantageous in that it is difficult to form a molecular filmuniformly.

SUMMARY OF THE INVENTION

A method for forming a molecular film of the present invention includesthe steps of: coating a surface of a substrate having active hydrogenatoms on its surface with a coating solution containing a silane-basedcompound having at least one reactive group selected from the groupconsisting of a chloro group, an alkoxy group and an isocyanate group;and effecting an elimination reaction between the active hydrogen atomson the surface of the substrate and the reactive groups of thesilane-based compounds, thereby covalently bonding the silane-basedcompounds to the surface of the substrate. The substrate is supplied toa chamber in which an atmosphere is maintained at a low water vapordensity, the surface of the substrate is coated with a coating solutioncontaining the silane-based compound and a solvent by using a transferelement. An elimination reaction is effected between the active hydrogenatoms and the reactive groups of the silane-based compounds. Thereafter,any coating solution containing unreacted silane-based compounds thatremains after coating is removed inside or outside the chamber.

In the above mentioned step, in the case where a chlorosilane compoundis used as the silane-based compound, a dehydrochlorination reaction iseffected as the elimination reaction. In the case where an alkoxysilanecompound is used, a dealcoholization reaction is effected.

In one embodiment according to the above-mentioned method of the presentinvention, the transfer element comprises an inner chamber enclosing atleast a portion where a coating solution is present in the transferelement. In this manner, hydrolysis of the silane-based compound in thecoating solution can be prevented.

In another embodiment according to the above-mentioned method of thepresent invention, air curtains for shutting off outside air areprovided at an inlet and an outlet of the chamber through which thesubstrate is introduced and withdrawn, respectively. In this manner,hydrolysis of the silane-based compound in the coating solution canfurther be prevented.

In still another embodiment according to the above-mentioned method ofthe present invention, the transfer element performs at least the stepsof applying the coating solution onto a support, and transferring thesolution applied to the support to the substrate on which a film is tobe formed. In this manner, the substrate can be uniformly coated withthe coating solution.

In yet another embodiment according to the above-mentioned method of thepresent invention, the transfer element is a roller coating element.This is most inexpensive. Furthermore, this method makes it possible todeal with a wide substrate having, for example, 1 to 10 m.

In another embodiment according to the above-mentioned method of thepresent invention, the silane-based compound comprises an alkyl group ora fluoroalkyl group. In particular, it is preferable to comprise anfluoroalkyl group, because a water-repelling property, an oil-repellingproperty and an antifouling property are improved.

In still another embodiment according to the above-mentioned method ofthe present invention, the solvent contains no active hydrogen atoms.This is preferable because a solvent having active hydrogen atoms reactswith the silane-based compound.

In yet another embodiment according to the above-mentioned method of thepresent invention, the solvent containing no active hydrogen atoms is atleast one selected from the group consisting of a hydrocarbon compound,a siloxane-based compound and hydrocarbon halide.

In another embodiment according to the above-mentioned method of thepresent invention, the mixing ratio of the silane-based compound to thesolvent in the coating solution is such that the silane-based compoundis present at an amount of 0.05 to 20% by weight, and the kinematicviscosity of the coating solution is 0.5 to 5000 cst (at 25° C.).

In still another embodiment according to the above-mentioned method ofthe present invention, the substrate is a glass sheet, and a face otherthan a face that is to be coated with the coating solution is maskedwith a resin film prior to coating. This is preferable because maskingperfectly protects the surface which is not to be coated, although thesurface which is not to be coated hardly reacts with the silane-basedcompound.

According to another aspect of the present invention, an apparatus forforming a molecular film includes a chamber including an element fortransporting a substrate from an inlet to an outlet, a transfer elementfor coating a surface of the substrate with a coating solutioncontaining silane-based compounds and a solvent, and an element formaintaining the atmosphere in the chamber at a low water vapor density.The apparatus further includes an element for removing any remainingcoating solution containing unreacted silane-based compounds after theprocess of coating inside or outside the chamber.

In one embodiment according to the above-mentioned apparatus of thepresent invention further includes an inner chamber enclosing at least aportion where a coating solution is present in the transfer element.

In another embodiment according to the above-mentioned apparatus of thepresent invention, air curtains for shutting off outside air areprovided at the inlet and the outlet of the chamber through which thesubstrate is introduced and withdrawn, respectively.

In still another embodiment according to the above-mentioned apparatusof the present invention, the element for maintaining the atmosphere ata low water vapor density is an element for introducing a gas having awater vapor density in the range from 0 to 0.0076 kg/m³.

In yet another embodiment according to the above-mentioned apparatus ofthe present invention, the transfer element performs at least the stepsof applying the coating solution onto a support, and transferring thesolution applied to the support to the substrate on which a film is tobe formed.

In another embodiment according to the above-mentioned apparatus of thepresent invention, the transfer element is a roller coating element.

In still another embodiment according to the above-mentioned apparatusof the present invention, the apparatus further includes an element forsupplying a gas having a low water vapor density in the inner chamber.

In yet another embodiment according to the above-mentioned apparatus ofthe present invention, the coating solution is applied to the support byattaching the solution onto the surface of the substrate by dropping thesolution onto the support, dipping the support in the solution, orcontacting the solution, or a vapor or spray of the solution with thesupport.

In another embodiment according to the above-mentioned apparatus of thepresent invention, the roller coating element includes at least a doctorroll for developing the coating solution, a coating roll for coating thesubstrate with the coating solution to a uniform thickness, and a backuproll for pressing the substrate from the lower face of the substrate.

In still another embodiment according to the above-mentioned apparatusof the present invention, the portion in the vicinity of the rolls wherethe water vapor density is controlled to be within the prescribed rangeis a space containing at least a portion where the solution is attachedto or stays on the surface of the rolls.

In yet another embodiment according to the above-mentioned apparatus ofthe present invention, the element for removing any remaining solutioncontaining unreacted silane-based compounds from the surface of thesubstrate is at least one selected from the group consisting of elementsfor removing by blowing a gas for evaporation, by heating forevaporation, by decompressing for evaporation, by blowing away with agas, and by washing away with a liquid.

Thus, the invention described herein makes possible the advantage ofproviding a method and an apparatus for producing a molecular filmneeding only a small amount of liquid to form a film, being capable ofdisregarding the pot life of a coating solution, facilitating theoperation of handling the substrate and reducing the cost as a whole.

These and other advantages of the present invention will become apparentto those skilled in the art upon reading and understanding the followingdetailed description with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the structure of a roller coatfilm-forming apparatus of an apparatus for producing a molecular film ofone example according to the present invention.

FIG. 2 is a schematic view showing the surface of a substrate when thesurface of the substrate is coated with a solution.

FIG. 3 is a schematic view showing an example of coating a substratewith a solution in a form different from that in FIG. 1.

FIG. 4 is a schematic view showing an example of coating a substratewith a solution using a fabric.

FIG. 5 is a schematic view showing a pad printing system.

FIG. 6 is a schematic view showing a process in which a liquid is usedas a support.

FIG. 7 is a schematic view of a roller coat film-forming apparatus of anapparatus for producing a molecular film of another example according tothe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the present invention, a molecular film having a thicknessin the range from about 0. nm to about 1 μm can be formed on a substrateby forming siloxane bonds between the substrate and silane-basedcompounds.

It is preferable that the silane-based compound be a compound comprisingan alkyl group or a fluoroalkyl group. A specific example of thecompound comprising a fluoroalkyl group includes a fluoroalkylsilanecompound expressed by a general formula C_(n) F_(2n+1) (CH₂)₂ SiCl₃ (n=apositive integer of 1 to 30), such asheptadecafluoro1,1,2,2,tetrahydrodecyl-trichlorosilane or the like.

As a solvent for dissolving the chlorosilane-based compound, any solventcan be used, as long as it does not contain active hydrogen atoms thatreact with the chlorosilane-based compound. For example, ahydrocarbon-based solvent, a hydrocarbon halide-based solvent, analkylsiloxane-based solvent, or a silicone oil-based solvent can be usedfor the fluoroalkylsilane compound. Specific examples of thehydrocarbon-based solvent include a solvent of oils expressed by ageneral formula C_(n) H_(2n+2) (n=a positive integer) such as aturpentine oil or the like, or expressed by a general formula C_(n)H_(2n). Specific examples of the hydrocarbon halide-based solventinclude a solvent expressed by a general formula C_(n) H_(2n-m+2) X_(m)(n=a positive integer, m=an integer, and X=halogen) such asoctadecafluorooctane or the like. Specific examples of thealkylsiloxane-based solvent include a linear silicone solvent expressedby a general formula R¹ (R² R³ SiO)_(n) R⁴ (n=a positive integer, R¹,R², R³, and R⁴ =alkyl groups) such as hexamethyldisiloxane or the like,or a cyclic silicone solvent expressed by a general formula (R¹ R²SiO)_(n) (n=a positive integer, R¹ and R² =alkyl groups) such asoctamethylsiloxane, or a mixture thereof.

Examples of a method for applying the solution containing thechlorosilane-based compound to the surface of a substrate include aroller coating method, a pad printing method or the like. In thesemethods, it is preferable that a portion of the apparatus where thesolution is present such as a roll, a pad or a substrate be maintainedat a water vapor density as low as 0 kg/m³ to 0.0076 kg/m³.

Examples of a chemical absorbent that can be used in the presentinvention are listed below:

(1) CH₃ (CH₂)_(r) SiX_(p) Cl_(3-p)

(2) CH₃ (CH₂)_(s) O(CH₂)_(t) SiX_(p) Cl_(3-p)

(3) CH₃ (CH₂)_(u) --Si(CH₃)₂ (CH₂)_(v) --SiX_(p) Cl_(3-p)

(4) CF₃ COO(CH₂)_(w) SiX_(p) Cl_(3-p)

(where p is an integer of 0 to 2, r is an integer of 1 to 25, s is aninteger of 0 to 12, t is an integer of 1 to 20, u is an integer of 0 to12, v is an integer of 1 to 20, and w is an integer of 1 to 25. X is ahydrogen, an alkyl group, an alkoxyl group, a fluorine containing alkylgroup, or a fluorine containing alkoxyl group.)

Furthermore, specific examples of the absorbent are the followingcompounds:

(5) CH₃ CH₂ O(CH₂)₁₅ SiCl₃

(6) CH₃ (CH₂)₂ Si(CH₃)₂ (CH₂)₁₅ SiCl₃

(7) CH₃ (CH₂)₆ Si(CH₃)₂ (CH₂)₉ SiCl₃

(8) CH₃ COO(CH₂)₁₅ SiCl₃

(9) CF₃ (CF₂)₇ --(CH₂)₂ --SiCl₃

(10) CF₃ (CF₂)₅ --(CH₂)₂ --SiCl₃

(11) CF₃ (CF₂)₇ --C₆ H₄ --SiCl₃

Furthermore, instead of the chlorosilane-based chemical absorbent asdescribed above, an isocyanate-based chemical absorbent obtained bysubstituting all of the chlorosilyl groups with isocyanate groups can beused. Examples thereof are as follows:

(12) CH₃ --(CH₂)_(r) SiX_(p) (NCO)_(3-p)

(13) CF₃ --(CH₂)_(r) SiX_(p) (NCO)_(3-p)

(14) CH₃ (CH₂)_(s) O(CH₂)_(t) SiX_(p) (NCO)_(3-p)

(15) CH₃ (CH₂)_(u) --Si(CH₃)₂ (CH₂)_(v) --SiX_(p) (NCO)_(3-p)

(16) CF₃ COO(CH₂)_(w) SiX_(p) (NCO)_(3-p)

(where, p, r, s, t, u, v, w and X are the same as above.)

Instead of the above-mentioned absorbents, the absorbent compoundsspecifically listed below can be used.

(17) CH₃ CH₂ O(CH₂)₁₅ Si(NCO)₃

(18) CH₃ (CH₂)₂ Si(CH₃)₂ (CH₂)₁₅ Si(NCO)₃

(19) CH₃ (CH₂)₆ Si(CH₃)₂ (CH₂)₉ Si(NCO)₃

(20) CH₃ COO(CH₂)₁₅ Si(NCO)₃

(21) CF₃ (CF₂)₇ --(CH₂)₂ --Si(NCO)₃

(22) CF₃ (CF₂)₅ --(CH₂)₂ --Si(NCO)₃

(23) CF₃ (CF₂)₇ --C₆ H₄ --Si(NCO)₃

Furthermore, as the chemical absorbent, in general, a substanceexpressed by a formula SiX_(k) (OA)_(4-k) (X is the same as above, A isan alkyl group, and k is 0, 1, 2, or 3) can be used. In particular, whena substance expressed by CF₃ --(CF₂)_(n) --(R)_(q) --SiX_(p) (OA)_(3-p)(n is a positive integer of 1 or more, preferably an integer of 1 to 22,R is an alkyl group, a vinyl group, an ethynyl group, an aryl group,silicon or substituent containing an oxygen atom, q is 0 or 1, and X, A,and p are the same as above) is used, a film having a more excellentantifouling property can be used. However, it is not limited thereto.Other examples are CH₃ --(CH₂)_(r) --SiX_(p) (OA)_(3-p) and CH₃--(CH₂)_(s) --O--(CH₂)_(t) --SiX_(p) (OA)_(3-p), CH₃ --(CH₂)_(u)--Si(CH₃)₂ --(CH₂)_(v) --SiX_(p) (OA)_(3-p), CF₃ COO--(CH₂)_(w)--SiX_(p) (OA)_(3-p), (where, p, r, s, t, u, v, w, X and A are the sameas above.)

Furthermore, more specific examples of the chemical absorbent are asfollows:

(24) CH₃ CH₂ O(CH₂)₁₅ Si(OCH₃)₃

(25) CF₃ CH₂ O(CH₂)₁₅ Si(OCH₃)₃

(26) CH₃ (CH₂)₂ Si(CH₃)₂ (CH₂)₁₅ Si(OCH₃)₃

(27) CH₃ (CH₂)₆ Si(CH₃)₂ (CH₂)₉ Si(OCH₃)₃

(28) CH₃ COO(CH₂)₁₅ Si(OCH₃)₃

(29) CF₃ (CF₂)₅ (CH₂)₂ Si(OCH₃)₃

(30) CF₃ (CF₂)₇ --C₆ H₄ --Si(OCH₃)₃

(31) CH₃ CH₂ O(CH₂)₁₅ Si(OC₂ H₅)₃

(32) CH₃ (CH₂)₂ Si(CH₃)₂ (CH₂)₁₅ Si(OC₂ H₅)₃

(33) CH₃ (CH₂)₆ Si(CH₃)₂ (CH₂)₉ Si(OC₂ H₅)₃

(34) CF₃ (CH₂)₆ Si(CH₃)₂ (CH₂)₉ Si(OC₂ H₅)₃

(35) CH₃ COO(CH₂)₁₅ Si(OC₂ H₅)₃

(36) CH₃ COO(CH₂)₁₅ Si(OC₂ H₅)₃

(37) CF₃ COO(CH₂)₁₅ Si(OCH₃)₃

(38) CF₃ (CF₂)₉ (CH₂)₂ Si(OC₂ H₅)₃

(39) CF₃ (CF₂)₇ (CH₂)₂ Si(OC₂ H₅)₃

(40) CF₃ (CF₂)₅ (CH₂)₂ Si(OC₂ H₅)₃

(41) CF₃ (CF₂)₇ C₆ H₄ Si(OC₂ H₅)₃

(42) CF₃ (CF₂)₉ (CH₂)₂ Si(OCH₃)₃

(43) CF₃ (CF₂)₅ (CH₂)₂ Si(OCH₃)₃

(44) CF₃ (CF₂)₇ (CH₂)₂ SiCH₃ (OC₂ H₅)₂

(45) CF₃ (CF₂)₇ (CH₂)₂ SiCH₃ (OCH₃)₂

(46) CF₃ (CF₂)₇ (CH₂)₂ Si(CH₃)₂ OC₂ H₅

(47) CF₃ (CF₂)₇ (CH₂)₂ Si(CH₃)₂ OCH₃

EXAMPLES

Hereinafter, the present invention will be specifically described by wayof examples with reference to the accompanying drawings.

Example 1

In this example, a method and an apparatus for producing a molecularfilm will be described by taking as an example a roller coatfilm-forming apparatus, which is one of the apparatus for producing afilm in accordance with the method for producing a film of the presentinvention. In addition, other methods also will be referred to, ifnecessary.

FIG. 1 is a schematic view showing the structure of a roller coatfilm-forming apparatus, which is one of the apparatus for producing afilm in accordance with the method for producing a film of the presentinvention. This roller coat film-forming apparatus 1 has the structurein which a substrate 2 is introduced from an inlet 3 to a chamber 11 anda substrate having a film formed thereon 5 exits from an outlet 4.Inside the apparatus is provided a doctor roll 6, a coating roll 7, atransporting roll 8, a nozzle 9 for dropping a chlorosilane-basedsolution, a nozzle 10 for supplying a gas having a prescribed watervapor density (a dry nitrogen gas), and a chamber 11 for maintaining theatmosphere at the prescribed water vapor density.

In the nozzle 9 for dropping a solution based on chlorosilane, a bottlefor storing the chlorosilane solution, a pump and a pipe for supplyingthe chlorosilane solution, a bottle for collecting waste liquid, areceiving member and a pipe for collecting waste liquid are provided.For the sake of simplicity, these members are not shown in FIG. 1.

In the roller coat film-forming apparatus, the coating roll 7 is incontact with or pressed onto the doctor roll 6, and a solutioncontaining chlorosilane-based compounds and a solvent is supplied to thecontact portion of the two rolls. By rotating the coating roll 7, thesolution is applied to the cylindrical surface of the coating roll 7.Then, the coating roll 7 is rotated in contact with or pressed onto thesurface of the substrate 2, so that the solution on the cylindricalsurface of the coating roll is transferred to the surface of thesubstrate. The substrate coated with the solution is transported to theoutlet 4 of the roller coat film-forming apparatus by the transportingroll 8. During this period, a gas (dry nitrogen gas) having a watervapor density maintained at the prescribed level is continuouslysupplied so that the solution or the solvent which has not contributedto the film-forming can be removed by natural evaporation.

In the operation described above, the reaction effected on the substratewill be described below. As the chlorosilane-based compound,heptadecafluoro1,1,2,2,tetrahydrodecyltrichlorosilane is used, andoctamethylcyclotetrasiloxane is used as the solvent. The concentrationof the chlorosilane-based compound of the solution is 1 vol. %. Thenozzle 9 is provided above the contact point of the coating roll 7 andthe doctor roll 6, and the solution is dropped from the nozzle 9. Thus,by rotating the coating roll, the solution is applied uniformly onto thecylindrical surface of the coating roll. The space surrounding thesolution, namely, the portion where the doctor roll, the coating rolland the nozzle are present, is covered with a cover and supplied with adry nitrogen gas. At this point, the water vapor density in the space is0.0075 kg/m³. By maintaining this water vapor density at this level, itis possible to prevent chlorosilyl groups in theheptadecafluoro1,1,2,2,tetrahydrodecyltrichlorosilane from beinghydrolyzed by water, and it is also possible to remove moisture on thesurfaces of the coating roll and the doctor roll and to prevent themoisture from being attached to the surfaces thereof. Furthermore, it ispossible to remove undesired moisture on the surfaces of the introducedsubstrate and to prevent moisture from being attached to the surfacethereof. In such a structure, the substrate is coated with the solutionapplied to the cylindrical surface of the coating roll by allowing thecoating roll to be in contact with or pressed onto the introducedsubstrate. FIG. 2 shows the surface of the substrate in this stage.Groups having active hydrogen atoms (hydroxyl groups 22 in FIG. 2) arepresent on the surface of the substrate 21. A dehydrochlorinationreaction is effected between the hydroxyl groups and a solute, e.g.,heptadecafluoro1,1,2,2,tetrahydrodecyltrichlorosilane (simply shown byellipses in FIG. 2) 24 in the coated solution 23, and then a thin film25 is formed of siloxane bonds to the surface of the substrate.Thereafter, in the case where solution that did not participate in thereaction is present on the substrate, the solution containing the soluteis removed from the surface of the substrate. In the case where thesolute reacted entirely, the solvent is removed from the surface of thesubstrate. The state shown herein is only one example for illustratingthe present invention, and the present invention is not limited thereto.A different alignment and orientation is possible. A thicker film thanin this example may be formed. In addition, it is believed that thereaction does not proceed from one side, as shown in FIG. 2, but thereaction for forming a film is effected simultaneously in severalportions on the substrate.

Now, another example of applying the solution to the substrate is shownin FIG. 3. In FIG. 1, the solution containing the chlorosilane-basedcompound and the solvent is dropped by the nozzle 9. In this example, adipping roll 31 is provided, and the dipping roll 31 is dipped in thesolution 32 in a container such as a vat or the like. This operationallows the cylindrical surface and the internal portion of the dippingroll to be impregnated with the solution. The dipping roll is allowed tobe in contact with the coating roll 33 so that the solution can betransferred onto the cylindrical surface of the coating roll and furtherthe surface of the substrate 34, as in the example of FIG. 1. In thismanner, a film is formed.

FIG. 4 shows another form of coating the solution using a fabric insteadof the rolls as shown in FIGS. 1 and 3. An endless band 41 is providedusing a guide, as shown in FIG. 4. A suitable example of this band is aband made of rubber, a fabric band having an impregnation property, orthe like. Apart of the band passes through a cloud chamber 42 containingthe solution, and then the band is allowed to be in contact with thesurface of the substrate 43 by a roll 44 so that the surface of thesubstrate can be coated with the solution applied to the band.Thereafter, the same processes as described referring to FIG. 1 areperformed.

The solution coated onto the surface of the substrate forms a filmthrough the reaction as shown in FIG. 2. In the example of FIG. 1, thesolution or the solvent which did not contribute to the film formationevaporates naturally on the transporting roll. In the case where thewater vapor density on the transporting roll exceeds the prescribedvalue, the chlorosilane-based compounds on the surface of the substratenot only react with hydroxyl groups on the surface of the substrate soas to form a film, but also react with each other, and are polymerizedby a chain reaction. In order to prevent the polymerization, it isnecessary to maintain the water vapor density at the prescribed value orless. Other methods than natural evaporation while maintaining theprescribed water vapor density or smaller are as follows: a method ofspraying a dry nitrogen gas which has been heated at the prescribedwater vapor density or less; a method for spraying a solution which isdissolved in the coating solution readily and is dried readily in themanner like a shower; a method of facilitating drying by putting thesubstrate under a reduced pressure on the way to the outlet; or a methodof drying by providing a high pressure stream of a dry gas at the outlet(referred to as air knife). The method of providing a high pressurestream of a dry gas at the outlet (air knife) is effective formaintaining the atmosphere at the prescribed water vapor density as wellas for drying the surface of the substrate. For this purpose, the highpressure stream of a dry gas is preferably provided not only at theoutlet, but also at the inlet.

Comparative Example 1

In order to confirm the effect of the production method of the presentinvention, a film having siloxane bonds is produced in a conventionalmethod. The importance of maintaining the water vapor density at a lowlevel has been described in Example 1. The case where the water vapordensity is not maintained at a low level also will be shown in thiscomparative example. Herein, a comparison is made in terms of the costby taking a conventional dip method as an example.

Heptadecafluoro1,1,2,2,tetrahydrodecyltrichlorosilane is used as thechlorosilane-based compound, and octamethylcyclotetrasiloxane is used asthe solvent, as used in Example 1. A 1 vol. % solution is prepared in avat. The atmosphere surrounding the vat containing the solution ismaintained at the above-mentioned water vapor density, and a glass plateof A4 size is dipped in the solution in the vat for 15 minutes.Thereafter, the solvent is dried naturally for 15 minutes.

A water droplet is dropped onto the surface of the glass plate on whicha film is formed, and the state of the surface is evaluated by an angleformed by the water droplet and the glass plate (contact angle).

The results of the comparison between Example 1 and Comparative Example1 are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                                   Conventional method                                             Method of Example 1                                                                         (Comparative Ex. 1)                                Comparison Items                                                                           (Roll-coating method)                                                                       (Dip method)                                       ______________________________________                                        Contact angle  112°      112°                                   Appearance observation                                                                     No attachment Opaque substance                                                              attached                                           Prepared liquid amount                                                                       0.4    g         200  g                                        Film-forming time                                                                            15     seconds   1800 seconds                                  ______________________________________                                    

Table 1 shows the results of the comparison regarding the contact angle,the appearance observation, the prepared liquid amount, and thefilm-forming time between a glass plate of A4 size having a film formedthereon by the method shown in Example 1 and a glass plate of A4 sizehaving a film formed thereon by the method shown in ComparativeExample 1. The contact angles of the obtained films are both 112°. Thismeans that the surface states are the same. On the other hand, in theappearance observation, since the water vapor density is not maintainedwithin the prescribed range after dipping, a large amount of opaquesubstances are attached onto the surface of the glass plate in theconventional method, whereas according to the method of the presentinvention, there is no attachment.

Furthermore, according to the method of the present invention, thesolution of the chlorosilane-based compound is used in an amount of 0.4g for one glass plate. On the other hand, the conventional methodrequires 200g, which is 500 times more, because the solution is preparedin a sufficient amount to dip the entire glass plate of A4 size. Thesolution in the conventional method can be used for another substrate tobe dipped in after the first one is dipped, because the solutioncontains a sufficient amount of chlorosilane-based compounds so as toform films. Thus, films can be formed on a plurality of substrates,though it is not certain that as many as 500 films can be formed.Nevertheless, according to the method of the present invention, everytime a film is to be formed, an appropriate amount of solution can beused for forming a film. In the conventional dip method, even if a filmis to be formed on only one substrate, it is necessary to prepare asolution in an amount of 200 g, as shown in this comparative example.Therefore, the method of the present invention is advantageous forforming a film in accordance with the requirements at the time of theproduction. Accordingly, the cost required for forming a film can bereduced. Furthermore, the method of the present invention isadvantageous in view of the keeping quality of the solution or the like.

Next, a clear difference is seen in the film-forming time. In Example 1of the present invention, a film is formed on one glass plate for 15seconds, and the film is defect-free in the appearance observation. Onthe other hand, the conventional dip method requires 1800 seconds, whichis 120 times longer, and the quality of the product is not satisfactory.In this point as well as, there is a significant difference in thenumber of films that can be formed in a predetermined time. Thisdemonstrates that the method of the present invention is advantageousfor reducing the cost.

Another difference between the method of the present invention and theconventional dip method is that a film is formed on one face of thesubstrate according to the method of the present invention, while a filmis formed on both faces of the substrate in the conventional method. Inthe case where a film is to be formed on only one face of the substratein the conventional method, it is necessary to previously cover the faceon which a film is not supposed to be formed with some element so thatthe reaction for forming a film cannot be effected. Furthermore, sincean unnecessary film is formed on the face on which a film is notsupposed to be formed in the conventional method, the cost for forming afilm is twice the cost of the film formed according to the method of thepresent invention.

Example 2

This example shows a pad printing method. FIG. 5 is a schematic view ofa pad printing system. Normal decyltrichlorosilane andheptadecafluoro1,1,2,2,tetrahydrodecyltrichlorosilane are used as thechlorosilane-based compounds. As the solvent, perfluorooctane is used.The solution concentration of each chlorosilane-based compound is 0.1vol. %. A glass container 51 containing the solution is provided in thechamber in which the water vapor density is maintained at 0.0071 kg/m³.A stamp-like pad tool 52 is used for the pad printing, and a rubbermember 53 is attached to the pad printing face thereof The size of therubber member is 30 mm×50 mm. This rubber face is dipped in the solutioncontaining normal decyltrichlorosilane. The rubber member can be asupport for transferring the solution to the substrate. Next, the rubberface is pressed onto a glass plate of A4 size 54 (as shown by the arrowin FIG. 5), so as to apply the solution to the glass plate surface.Then, the glass plate is allowed to stand until the solvent is driednaturally from the glass plate surface. Similarly, the surface of aglass plate is coated with aheptadecafluoro1,1,2,2,tetrahydrodecyltrichlorosilane solution usinganother pad tool, and the glass plate is allowed to stand until thesolvent is dried naturally. These processes are performed in a chamberwith a water vapor density of 0.0071 kg/m³ maintained by a dry air. Theglass plates having been subjected to the above-mentioned processes aretaken out from the chamber in which the water vapor density iscontrolled, and the contact angles are measured with water droplets inthe same manner as described above.

The contact angle in the portion where a film made of normaldecyltrichlorosilane is formed is 100°, while the contact angle in theportion where a film made of heptadecafluorol,1,2,2,tetrahydrodecyltrichlorosilane is formed is 111°. This differencein the contact angles is due to the materials. On the other hand, thecontact angle in the portion where a film is not formed is 30° or less.Furthermore, when the glass plate on which a film is formed by the padprinting method is immersed in water, and withdrawn from the water, theportion where a film is formed in a shape of 30 mm×50 mm repels waterand the portion where the film is not formed gets wet. Thus, using thepad printing method, a film can be formed only in the portion where afilm is required to be formed, and a glass substrate having a differentstate from that obtained by the roller coat method described in Example1 can be obtained.

Example 3

In all the above-described examples, the supports were solid. The casewhere the support is liquid will be described in this example.

FIG. 6 is a schematic view showing processes where the support isliquid. Normal octadecyltrichlorosilane is used as thechlorosilane-based compound, and a linear silicone oil mixture (straightdimethyl silicone oil manufactured by Toray-Dow Corning Silicone Co.,Ltd.) is used as the solvent. Thus, a solution 61 having a concentrationof 0.1 vol. % is prepared. For the support, a liquid incompatible withthe linear silicone oil mixture and normal octadecyltrichlorosilane isrequired. In this example, a liquid based on fluorine 62 (Fluorinert(trademark) manufactured by Sumitomo 3M Limited) is used. A square vat63 of 15 cm×15 cm is provided in a closed space having a water vapordensity of 0.0063 kg/m³ maintained. The liquid based on fluorine ispoured into the vat to a sufficient level, and the solution containingthe normal octadecyltrichlorosilane and the linear silicone oil mixtureis quietly dropped in an amount of about 10 ml.

The solution is dropped uniformly onto the liquid based on fluorine. Asilicon substrate 64 having a diameter of 3 inches is dipped in the vat,and is withdrawn immediately (in the direction shown by the arrow inFIG. 6), and is dried until the solvent evaporates. Thus, a film formedof normal octadecyltrichlorosilane is formed on the silicon substrate.

In the above examples, the glass substrate and the silicon substrate areused. However, any material can be used, as long as the material hasactive hydrogen atoms on its surface. A metal, a metal oxide, ceramics,plastics or the like that satisfy the above mentioned requirement areeffective.

Furthermore, in this example, a gas supply nozzle for maintaining thewater vapor density at a prescribed 0 to 0.0076 kg/m³ is shown. However,other methods can be used, as long as the water vapor density iscontrolled to be at the prescribed level, for example, by the provisionof a moisture absorbing apparatus, without supplying a gas as in thisexample. Furthermore, in the case of the gas supply system or the like,it may be necessary to provide an exhauster. In this example, such adevice is omitted.

Example 4

FIG. 7 is a schematic view showing the structure of a roller coater asone apparatus for producing a film employing a transfer method. Achamber 71 in this roller coater 70 includes an inlet 72 and an outlet73 through which a substrate 81 is introduced and withdrawn,respectively, and includes components such as a doctor roll 74, acoating roll 75 and a backup roll 87 therein. The substrate introducedfrom the inlet 72 is transported by a transporting member such as a roll76 or the like, so as to pass through the coating roll 75 and exit fromthe outlet 73. A container 77 contains a solution 78 containingsilane-based compounds to be coated on the substrate. The solution 78 isdrawn by a pipe 80a provided with a pump 79, and supplied through a pipe80b to the contact area between the outer faces of the doctor roll 74and the coating roll 75. A gas (preferably, a dry nitrogen gas or dryair) having a low water vapor density is supplied to the inlet 72 andthe outlet 73, as shown by 82 and 83 in FIG. 7, so as to form aircurtains 84 and 85. Furthermore, a cover 86 for covering the upperportions of the doctor roll 74 and the coating roll 75 (an innerchamber) is provided, and a gas (preferably, a dry nitrogen gas or dryair) having a low water vapor density 89 is supplied from a pipe 88 tothe inner chamber, so that the atmosphere surrounding the doctor rolland the coating roll is maintained at a low humidity, preferably a watervapor density of 0.0076 kg/m³ or less (corresponding to a relative watervapor density of 35% or less at 25° C.). Although the apparatus lookssealed except for the inlet and the outlet in FIG. 7, a suitableventilation path for discharging a solvent or the like is provided.

In the roller coater, the coating roll 75 is in contact with or pressedonto the doctor roll 74, and the solution containing a silane-basedcompound is supplied to this contact area. By rotating the coating roll75, the solution is attached to the outer cylindrical face of thecoating roll 75. Furthermore, the coating roll 75 is rotated in contactwith or pressed onto the surface of the substrate 81, so that thesurface of the substrate 81 can be coated with the solution uniformly.Since the atmosphere inside the apparatus is maintained at a low watervapor density, the silane-based compounds coated on the substrate areprevented from reacting with moisture before the dehydrochlorinationreaction.

As described above, according to the present invention, while supplyinga solution containing at least a silane-based compound to the outercylindrical face of the coating roll of the roller coater at theatmosphere of a low water vapor density, the coating roll is rotated incontact with or pressed onto the surface of the substrate, so that thesurface of the substrate is coated with the solution (shown in (A) inFIG. 7). At this time, the silane-based compounds and the hydroxylgroups on the surface effect the condensation reaction, and formcovalent bonds, as shown in Formula 1 below. ##STR1## Thereafter, thesubstrate is dried at the atmosphere with a low water vapor densitymaintained inside the roller coater, and the coated solution comprisingthe solvent and any silane-based compounds not bonded to the hydroxylgroups on the substrate evaporates so as to be removed (shown in (B) inFIG. 7). Thus, only the silane-based compounds covalently bonded to thesurface of the substrate remain on the substrate. Furthermore, when thissubstrate is contacted with the atmosphere containing moisture outsidethe roller coater, hydrolysis is effected as in the manner shown inFormula 2 below: ##STR2##

Next, when the substrate is dried under a dry atmosphere (shown in (C)in FIG. 7), the condensation reaction is effected among the silane-basedcompounds, as shown in Formula 3 below, so that a film is formed ofcovalent bonds to the surface of the substrate via siloxane bonds.##STR3##

The process shown in (B) in FIG. 7 can be carried out outside thechamber 71.

A film having siloxane bonds is produced using the above-mentionedapparatus. More specifically, the coating roll 75 and the doctor roll 74are formed of isobutylene-isoprene rubber. For the silane-basedcompound, fluoroalkyltrichlorosilane expressed by a formula C₈ F₁₇(CH₂)₂ SiCl₃ is used. For the solvent, octamethyl-cyclotetrasiloxane,which is nonaqueous, is used, so that a 1 vol. % solution of the silaneis prepared. In order to maintain the atmosphere surrounding the coatingroll 75 and the doctor roll 74 and the atmosphere inside the rollercoater 70 at a low water vapor density, a nitrogen gas having a watervapor density 0.03 kg/m³ or less is supplied.

A float glass as the substrate 81 is introduced to the roller coaterwith one face facing up so that a film of the silane-based compounds canbe formed on the upper face. The lower face of the float glass iscovered with a cover film made of polyethylene terephthalate so as notto be in contact with the silane-based compounds. When the glasssubstrate is introduced into the chamber, the surface of the float glassis coated with the solution uniformly to a thickness of about 0.5 to 1μm at room temperature by adjusting the extent of pressing the coatingroll 75 to the doctor roll 74 and the substrate 81. Thereafter, thefloat glass is dried with a nitrogen gas having a water vapor density0.03 kg/m³ or less at the position shown by (B) in FIG. 7. Furthermore,the float glass is taken out from the chamber, and dried in theatmosphere containing moisture. Under the presence of the moisture, thecondensation reaction is effected among the silane-based compoundscoated on the float glass, so that a film is formed on the surface ofthe substrate as a result of covalent bonds via the siloxane bonds.Thereafter, the cover film covering the lower face of the substrate isremoved. This float glass is advantageously used as a laminated glass,which can be formed by attaching the float glasses with the faces havingcovalent bonds of the residues of the silane-based compounds, whichrepel water and oil, outward, and the faces masked with the cover filminward.

As described above, the method for forming a film according to thepresent invention makes it possible to form a film on the flatsubstrate, to improve the productivity significantly and thus to reducethe production cost significantly, compared with the conventional dipmethod. Thus, the industrial value thereof is great.

The invention may be embodied in other forms without departing from thespirit or essential characteristics thereof. The embodiments disclosedin this application are to be considered in all respects as illustrativeand not limitative, the scope of the invention is indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

What is claimed is:
 1. A method for forming a molecular film comprisingthe steps of: coating a surface of a substrate having active hydrogenatoms on its surface with a coating solution containing a silane-basedcompound having at least one reactive group selected from the groupconsisting of a chloro group, an alkoxy group and an isocyanate group;and effecting an elimination reaction between the active hydrogen atomson the surface of the substrate and reactive groups of the silane-basedcompound, thereby covalently bonding the silane-based compounds to thesurface of the substrate,wherein the substrate is supplied to a chamberin which an atmosphere is maintained at a water vapor density in therange of 0 to 0.0076 kg/m³, the surface of the substrate is coated witha coating solution containing the silane-based compound and a solvent byusing a transfer element, an elimination reaction is effected betweenthe active hydrogen atoms and the reactive groups of the silane-basedcompounds, and thereafter, any coating solution containing unreactedsilane-based compounds after coating is removed.
 2. The method forforming a molecular film according to claim 1, wherein the transferelement comprises an inner chamber enclosing at least a portion where acoating solution is present on the transfer element.
 3. The method forforming a molecular film according to claim 1, wherein air curtains forshutting off outside air are provided at an inlet and an outlet of thechamber through which the substrate is introduced and withdrawn,respectively.
 4. The method for forming a molecular film according toclaim 1, wherein the transfer element performs at least the steps ofapplying the coating solution to a support, and transferring thesolution applied to the support to the substrate on which a film is tobe formed.
 5. A The method for forming a molecular film according toclaim 1, wherein the transfer element is a roller coating element. 6.The method for forming a molecular film according to claim 1, whereinthe silane-based compound comprises an alkyl group or a fluoroalkylgroup.
 7. The method for forming a molecular film according to claim 1,wherein the solvent contains no active hydrogen atoms.
 8. The method forforming a molecular film according to claim 7, wherein the solventcontaining no active hydrogen atoms is at least one selected from thegroup consisting of a hydrocarbon compound, a siloxane-based compoundand hydrocarbon halide.
 9. The method for forming a molecular filmaccording to claim 1, wherein a mixing ratio of the silane-basedcompound to the solvent in the coating solution is such that thesilane-based compound is present at an amount of 0.05 to 20% by weight,and the kinematic viscosity of the coating solution is 0.5 to 5000 cst(at 25° C.).
 10. The method for forming a molecular film according toclaim 1, wherein the substrate is a glass sheet, and a face other than aface which is to be coated with the coating solution is masked with aresin film prior to coating.